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Nitric acid oxidizes iodine to iodic acid, $\ce{HIO3}$ and not periodic acid, $\ce{HIO4}$, which is of a higher oxidation state. This happens although other nonmetals are oxidized to their highest oxidation state. How can this be explained?

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  • $\begingroup$ Can u pls give a balanced chemical equation for the reaction of I2 with conc HNO3. $\endgroup$ – Yashwini Aug 21 '20 at 18:34
  • $\begingroup$ @Yashwini Sorry. This was a long time back. I am majoring in a completely different field for more than three years $\endgroup$ – Aaron John Sabu Aug 21 '20 at 19:23
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Nitric acid is not strongly oxidizing enough to get iodine to +7. Relativistic effects tend to make the $s$ subshell valence electrons more stable than the others in heavy atoms (http://www.annualreviews.org/doi/abs/10.1146/annurev-physchem-032511-143755), so to some extent iodine acts as if it has only five valence electrons. To pull out those last two electrons and get periodic acid, electrochemical oxidation is commonly used with a very high oxidation potential (https://en.wikipedia.org/wiki/Periodic_acid).

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  • $\begingroup$ Can u pls give a balanced chemical equation for the reaction of I2 with conc HNO3. $\endgroup$ – Yashwini Aug 21 '20 at 18:34
  • $\begingroup$ Can u pls ask this as another question? $\endgroup$ – Oscar Lanzi Aug 21 '20 at 18:53

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